1. Field of the Invention
The present invention relates to a battery protection IC chip, and particularly relates to a battery protection IC chip that constitutes a battery pack protection circuit capable of preventing a lithium-ion battery used as a power source for a mobile device from overcharge, overdischarge, and overcurrent.
2. Description of the Related Art
Many mobile devices employ lithium-ion batteries in their battery packs. Lithium-ion batteries are likely to have troubles in the event of overcharge, overdischarge, and overcurrent. Therefore, battery packs for lithium-ion batteries are provided with battery protection modules including battery protection circuits that prevent lithium-ion batteries from overcharge, overdischarge, and overcurrent. Such a battery protection circuit has a FET chip serving as an electronic switch that opens in response to overcharge, overdischarge, and overcurrent. The battery protection module includes a COB (Chip On Board) structure in which chips and wires are encapsulated by a synthetic resin part, and a discrete module structure in which a packaged element is installed. The battery packs are repeatedly rechargeable by an associated recharger.
[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-6524
There is a high risk of trouble if an overcurrent is applied to a lithium-ion battery from a recharger during charging, or if an overcurrent is applied to a mobile device from a lithium-ion battery during use of the mobile device. It is therefore preferable from a safety standpoint to take some measures against these events. For example, because a FET chip generates heat in the case of overcurrent, detecting the temperature of the FET chip and turning off the FET chip when the temperature of the FET chip rises to a predetermined temperature may be one of the measures. It is desirable to provide such a measure with no increase in production costs of battery protection modules, no additional parts, and a high detection accuracy.